Swollen River Mussel, Unio tumidus

The Swollen River Mussel, Unio Tumidus, is a species of freshwater mussel, an aquatic bivalve mollusk belonging to the family Unionidae, the river mussels.

Its native distribution is European. The distribution range also includes Croatia, Czech Republic, Germany, British Isles, Sweden, Poland, Slovakia, Lithuania, Netherlands, and Latvia.

Image Caption: Shell of Unio tumidus from the Netherlands. Credit: Emma Versteegh/Wikipedia (CC BY-SA 3.0)